feat: Improve withdraw-all-rewards UX (cosmos#9781)

## Description
Related to cosmos#9489, this PR improves the UX when using the `withdraw-all-rewards` command by forcing the broadcast mode to `block` if the chunk size is greater than 0. This will ensure that the transactions do not fail even if the user uses invalid broadcast modes for this command (`sync` and `async`). 

---

### Author Checklist

*All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.*

I have...

- [x] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [x] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#pr-targeting))
- [x] provided a link to the relevant issue or specification
- [x] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [x] updated the relevant documentation or specification
- [x] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

*All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

CHANGELOG.md

@@ -65,6 +65,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 ### Client Breaking Changes
 
 * [\#9594](https://github.com/cosmos/cosmos-sdk/pull/9594) Remove legacy REST API. Please see the [REST Endpoints Migration guide](https://docs.cosmos.network/master/migrations/rest.html) to migrate to the new REST endpoints.
+* [\#9781](https://github.com/cosmos/cosmos-sdk/pull/9781) Improve`withdraw-all-rewards` UX when broadcast mode `async` or `async` is used.
 
 
 ### CLI Breaking Changes

x/distribution/client/cli/tx.go

@@ -23,7 +23,7 @@ var (
 )
 
 const (
-	MaxMessagesPerTxDefault = 5
+	MaxMessagesPerTxDefault = 0
 )
 
 // NewTxCmd returns a root CLI command handler for all x/distribution transaction commands.
@@ -126,11 +126,12 @@ func NewWithdrawAllRewardsCmd() *cobra.Command {
 		Short: "withdraw all delegations rewards for a delegator",
 		Long: strings.TrimSpace(
 			fmt.Sprintf(`Withdraw all rewards for a single delegator.
+Note that if you use this command with --%[2]s=%[3]s or --%[2]s=%[4]s, the %[5]s flag will automatically be set to 0.
 
 Example:
-$ %s tx distribution withdraw-all-rewards --from mykey
+$ %[1]s tx distribution withdraw-all-rewards --from mykey
 `,
-				version.AppName,
+				version.AppName, flags.FlagBroadcastMode, flags.BroadcastSync, flags.BroadcastAsync, FlagMaxMessagesPerTx,
 			),
 		),
 		Args: cobra.NoArgs,
@@ -167,6 +168,11 @@ $ %s tx distribution withdraw-all-rewards --from mykey
 			}
 
 			chunkSize, _ := cmd.Flags().GetInt(FlagMaxMessagesPerTx)
+			if clientCtx.BroadcastMode != flags.BroadcastBlock && chunkSize > 0 {
+				return fmt.Errorf("cannot use broadcast mode %[1]s with %[2]s != 0",
+					clientCtx.BroadcastMode, FlagMaxMessagesPerTx)
+			}
+
 			return newSplitAndApply(tx.GenerateOrBroadcastTxCLI, clientCtx, cmd.Flags(), msgs, chunkSize)
 		},
 	}